Transportation devices including conveyor belts are widely used as item transportation means in various industrial fields such as steel, coal, and cement. As larger transportation volumes and longer transportation paths are required in recent years, there is strong demand to reduce power consumption (save energy) in such transportation devices. A conveyor belt is typically composed of lower cover rubber, a reinforcing member made of steel cords or the like, and upper cover rubber. Of these members, the lower cover rubber has particularly significant influence on energy saving performance as it comes into contact with a driving pulley, a driven pulley, a shape retaining roller, etc.
Meanwhile, it is also important for the conveyor belt to have basic mechanical properties such as breaking resistance as a transportation device member, for stable operation and long life.
In view of the above, the rubber composition used in a rubber member such as the lower cover rubber needs to be improved to provide such a conveyor belt that contributes to lower power consumption of the transportation device without impairing basic mechanical properties such as breaking resistance as a transportation device member (Patent Literature (PTL) 1).